Platform unit for combined sensing of pressure, temperature and humidity

ABSTRACT

A modular platform unit comprising a plurality of sensors for the combined sensing of pressure, temperature and humidity. In particular, the sensors are composed of a layer of metallic-capped nanoparticles (MCNP) casted on a flexible substrate or a rigid substrate. Integration of the platform unit for artificial or electronic skin applications is disclosed.

This application is divisional application of U.S. Ser. No. 14/387,838filed on Sep. 24, 2014, which is a national stage application under 371of PCT/1132013/052235 filed Mar. 21, 2013, which claims priority to U.S.Ser. No. 61/783,614 filed Mar. 14, 2013 and U.S. Ser. No. 61/615,475filed Mar. 26 2012. The disclosure of all applications are incorporatedby reference in their entirety.

FIELD OF THE INVENTION

The present invention is directed to a platform unit comprising aplurality of sensors comprising metallic nanoparticles capped with anorganic coating for detecting pressure, temperature and humidity.

BACKGROUND OF THE INVENTION

Production of biomimetic artificial or electronic skin requireslarge-scale sensor arrays that are capable of sensing pressure, humidityand temperature with high resolution and low response times. Thesesensor arrays, designed to provide physical and chemical information ofthe environment can be utilized by a variety of applications such asmedical prosthesis and robotics industries. For example, prostheticlimbs can be covered with artificial or electronic skin to provide theuser with a sense of touch in the form of different pressure levels, androbotic limbs can be integrated with artificial or electronic skinsurface of varying sensitivities to allow autonomous control forhandling objects. Robotic surgeries, health monitoring and many otherpotential applications, can benefit from the use of artificial orelectronic skin having varying sensitivities to pressure, temperature,and/or humidity conditions (Eltaib et al., Mechatronics 2003, 13,1163-1177; Lee et al., Mechatronics 1999, 9, 1-31; and Dargahi et al.,Int. J. Med. Rob. Comp. Ass. Surg. 2004, 1, 23-35).

Flexible sensors, originally designed as soft and rubbery components ofhand-held consumer electronics and displays, are now being explored foruse as ultrathin health-monitoring tapes that could be mounted onto theskin (Tiwana et al., Sens. Actuat. A 2012, 179, 17-31; and Rogers etal., PNAS, 2009, 106, 10875-10876). Low-power touch-sensitive platformsof flexible sensors that are based on nanowires, carbon nanotubes,nanoparticles, rubber dielectric layers, and organic field-effecttransistors, have been successfully demonstrated (Takci et al., NatureMater. 2010, 9, 821-826; Herrmann et al., Appl. Phys. Lett. 2007, 91,183105; Siffalovic et al., Nanotech. 2010, 21, 385702; Vossmeyer et al.,Adv. Funct. Mater. 2008, 18, 1611-1616; Maheshwari et al., Science,2006, 312, 1501-1504; Mannsfeld et al., Nature Mater. 2010, 9, 859-864;Pang et al., Nature Mater. 2012, 11, 795-801; Matsuzaki et al., Sens.Actuat. A 2008, 148, 1-9; Lacour et al., Annual International Conferenceof the IEEE on Engineering in Medicine and Biology Society (EMBC), 2011,8373-8376; Someya et al., PNAS 2004, 101, 9966-9970; Cosseddu et al.,IEEE Elec. Dev. Lett. 2012, 33, 113-115; Joseph et al., J. Phys. Chem. C2008, 112, 12507-12514; Boland, J. Nat. Mater. 2010, 9, 790-792; andYu-Jen et al., IEEE Elec. Dev. Lett. 2011, 58, 910-917).

US 2011/0019373 discloses an arrangement for sensing ambient conditionsin electric equipment and/or for sensing biometric variables of a user,preferably applied in mobile terminals.

US 2012/0062245 discloses an apparatus comprising: a dielectricstructure including a plurality of elastomeric regions separated fromone another by space regions, the elastomeric regions being configuredand arranged. in response to pressure, to compress and thereby exhibit achanged effective dielectric constant corresponding to a state ofcompression of the elastomeric regions; and a sense circuit including aplurality of impedance-based sensors, each impedance-based sensorincluding a portion of the dielectric structure and configured andarranged to respond to the change in dielectric constant by providing anindication of the pressure applied to the dielectric structure adjacenteach sensor.

In order to achieve wide range implementation of flexible sensors asartificial or electronic skin, several requirements have to be met.First, these sensors need to afford a wide dynamic range that willenable measuring both low pressures (i.e. 1-10 KPa) for small objectmanipulation as well as high pressures (i.e. 10-100 KPa) formanipulating heavy objects. Second, these sensors require thesimultaneous. measurement of pressure (touch), humidity, temperatureand/or the presence of chemical compounds (Arregui et al., IEEE SensorsJ. 2002, 2, 482-487; Cook et al., JPMC 2009, 5, 277-298; Shunfeng etal., IEEE Sensors J. 2012, 10, 856-862; Lopez-Higuera et al., J.Lightwave Tech. 2011, 29, 587-608; Konvalina et al., ACS Appl. Mater.Interf. 2012, 4, 317-325; Bay et al., J. S. Rob. Autom. Mag. IEEE 1995,2, 36-43; and Wang et al., Langmuir 2010, 26, 618-632). Additionalrequirements include low-voltage/low power operation (typically below5V), to be compatible with commonly used batteries of portable devices(Tsung-Ching et al., J. Disp. Tech. 2009, 5, 206-215). Finally, thesesensors require easier, faster, and more cost-effective fabricationtechniques to afford their wide application.

Layers of metallic-capped nanoparticles (MCNPs) on flexible substratesare potential candidates for a new generation of highly sensitiveflexible sensors that meet these requirements (Herrmann et al., Appl.Phys. Lett. 2007, 91, 183105; Wang et al., Langmuir 2010, 26, 618-632;Wuelfing et al., J. Phys. Chem. B 2002, 106, 3139-3145; Haick, J. Phys.D 2007, 40, 7173-7186; Tisch et al., MRS Bull. 2010, 35, 797-803; Tischet al., Rev. Chem. Eng. 2010, 26, 171-179; Vossmeyer et al., Adv. Funct.Mater. 2008, 18, 1611-1616; Farcau et al., J. Phys. Chem. C. 2011, 115,14494-14499; and Farcau et al., ACS Nano 2011, 5, 7137-7143). Theelectrical properties of MCNP films exponentially depend on theinter-particle distance. Thus, deposition of the MCNPs on a flexiblesubstrate allows modulating the resistance either by stretching or bybending the substrate. Geometry and mechanical properties of thesubstrate also affect the inter-particle separation. For example,metal-enhanced fluorescence, optical properties, and small-angle X-rayspectroscopy (SAXS) studies have shown that the nanoparticle separationdepends on the substrate strain. Moreover, theoretical calculations haveshown that the sensitivity of individual sensors to tactile load can beadjusted by controlling the thickness of the substrate.

WO 2009/066293, WO 2009/118739, WO 2010/079490, WO 2011/148371, WO2012/023138, US 2012/0245434, US 2012/0245854, and US 2013/0034910 tosome of the inventors of the present invention disclose apparatusesbased on nanoparticle conductive cores capped with an organic coatingfor detecting volatile and non-volatile compounds, particularly fordiagnosis of various diseases and disorders.

There remains an unmet need for the combined sensing of pressure,temperatures and humidity for multi-functional electronic or artificialskin applications.

SUMMARY OF THE INVENTION

The present invention provides a platform unit for detecting pressure,temperature and humidity using sensor technology which is based onmetallic nanoparticles capped with an organic coating.

The present invention is based in part on the unexpected finding thatsensors of metallic-capped nanoparticles (MCNPs) can be used as pressuresensors when deposited on flexible substrates. These sensors allow thedetection of a wide range of loads when using substrates havingdifferent geometrical and mechanical properties. Surprisingly, thesesensors further provide highly sensitive temperature and humiditymeasurements thereby enabling the combined detection of physical andchemical environmental parameters. These results provide a new avenue totailor the sensing properties of a modular matrix of MCNP sensors toafford their use as artificial or electronic skin.

According to a first aspect, the present invention provides a platformunit for detecting a parameter selected from the group consisting ofpressure, temperature, humidity and a combination thereof, the platformunit comprising: a plurality of sensors comprising metallicnanoparticles capped with an organic coating, wherein the plurality ofsensors comprise: at least one pressure sensor being deposited on asubstantially flexible substrate, wherein the pressure sensor isconfigured to sense pressure applied thereon and to generate anelectrical signal in response thereto, and at least one temperature orhumidity sensor configured to exhibit a change in conformation of themetallic nanoparticles capped with an organic coating in response to achange in temperature or a change in humidity and generate an electricalsignal in response thereto, thereby providing the detection of pressure,temperature, humidity or their combination. In one embodiment, theplatform unit provides the concurrent detection of pressure, temperatureand humidity.

In certain embodiments, the platform unit comprises at least threesensors comprising metallic nanoparticles capped with an organiccoating, wherein the three sensors comprise a pressure sensor beingdeposited on a substantially flexible substrate, wherein the pressuresensor is configured to sense pressure applied thereon and to generatean electrical signal in response thereto, a temperature sensorconfigured to exhibit a change in conformation of the metallicnanoparticles capped with an organic coating in response to a change intemperature and generate an electrical signal in response thereto, and ahumidity sensor configured to exhibit a change in conformation of themetallic nanoparticles capped with an organic coating in response to achange in humidity and generate an electrical signal in responsethereto.

In some embodiments, the temperature and humidity sensors are configuredto exhibit an independent change in conformation of the metallicnanoparticles capped with an organic coating in response to each of achange in temperature or a change in humidity.

In certain embodiments, the substantially flexible substrate comprises apolymer. In specific embodiments, the polymer is selected from the groupconsisting of polyimide, polyamide, polyimine, polyethylene, polyester,polydimethylsiloxane, polyvinyl chloride, and polystyrene. Eachpossibility represents a separate embodiment of the present invention.In other embodiments, the substantially flexible substrate comprises asilicon rubber. In yet other embodiments, the substantially flexiblesubstrate comprises silicon dioxide. It will be recognized by one ofskill in the art that by changing the material which forms thesubstantially flexible substrate, different load sensitivities of thepressure sensor can be obtained.

In other embodiments, the substantially flexible substrate ischaracterized by widths in the range of about 0.01-10 cm and thicknessesin the range of about 20-500 μm. It will be recognized by one of skillin the art that the geometrical parameters of the substantially flexiblesubstrate can be used to control the load sensitivity of the pressuresensor.

In various embodiments, the pressure sensor is configured to generate anelectrical signal which is proportional to the amount of deflection ofthe substantially flexible substrate. In other embodiments, the pressuresensor is configured as a strain gauge which translates the mechanicaldeflection into an electrical signal.

In further embodiments, the temperature or humidity sensors aredeposited on a substantially flexible or substantially rigid substrate.Each possibility represents a separate embodiment of the presentinvention. In some embodiments, the substantially flexible substrate onwhich the temperature or humidity sensors are deposited comprises apolymer selected from the group consisting of polyimide, polyamide,polyimine, polyethylene, polyester, polydimethylsiloxane, polyvinylchloride, and polystyrene. Each possibility represents a separateembodiment of the present invention. In yet other embodiments, thesubstantially flexible or rigid substrate on which the temperature orhumidity sensors are deposited comprises silicon dioxide. In otherembodiments, the substantially flexible substrate comprises a siliconrubber. In certain embodiments, the substantially rigid substrate isselected from the group consisting of metals, insulators,semiconductors, semimetals, and combinations thereof. Each possibilityrepresents a separate embodiment of the present invention. In oneembodiment, the substantially rigid substrate comprises silicon dioxideon a silicon wafer. In another embodiment, the substantially rigidsubstrate comprises a substantially rigid polymer. In yet anotherembodiment, the substantially rigid substrate comprises indium tinoxide.

In additional embodiments, the platform unit comprises a plurality ofelectrodes comprising an electrically conductive material, coupled toeach sensor for measuring the signals generated by the sensors. Invarious embodiments, the distance between adjacent electrodes rangesbetween about 0.01 mm and about 5 mm. It will be recognized by one ofskill in the art that the distance between adjacent electrodes whichdefines the sensing area can be used to control the sensitivity of thesensors to changes in load, temperature and/or humidity.

In some embodiments, each sensor in the platform unit is configured in aform selected from the group consisting of a capacitive sensor, aresistive sensor, a chemiresistive sensor, an impedance sensor, and afield effect transistor sensor. Each possibility represents a separateembodiment of the present invention. In exemplary embodiments, eachsensor in the platform unit is configured as a chemiresistor.

In various embodiments, the platform unit further comprises a detectionmeans comprising a device for measuring changes in resistance,conductance, alternating current (AC), frequency, capacitance,impedance, inductance, mobility, electrical potential, optical propertyor voltage threshold. Each possibility represents a separate embodimentof the present invention.

In yet other embodiments, the metallic nanoparticles are selected fromthe group consisting of Au, Ag, Ni, Co, Pt, Pd, Cu, Al, and combinationsthereof. Each possibility represents a separate embodiment of thepresent invention. In additional embodiments, the metallic nanoparticlesare metallic alloys selected from the group consisting of Au/Ag, Au/Cu,Au/Ag/Cu, Au/Pt, Au/Pd, Au/Ag/Cu/Pd, Pt/Rh, Ni/Co, and Pt/Ni/Fe. Eachpossibility represents a separate embodiment of the present invention.In an exemplary embodiment, the metallic nanoparticles are gold (Au)nanoparticles.

In other embodiments, the metallic nanoparticles have a geometryselected from the group consisting of a cubic, a spherical, and aspheroidal geometry. Each possibility represents a separate embodimentof the present invention.

In further embodiments, the organic coating comprises compounds selectedfrom the group consisting of alkylthiols, arylthiols, alkylarylthiols,alkylthiolates, ω-functionalized alkanethiolates, arenethiolates,(γ-mercaptopropyl)tri-methyloxysilane, dialkyl disulfides andcombinations and derivatives thereof. Each possibility represents aseparate embodiment of the present invention. In an exemplaryembodiment, the organic coating is2-nitro-4-trifluoro-methylbenzenethiol. In another exemplary embodiment,the organic coating is 3-ethoxythiophenol. In yet another exemplaryembodiment, the organic coating is decanethiol. In further exemplaryembodiments, the organic coating is dodecylamine. In variousembodiments, the organic coating is characterized by a thickness rangingfrom about lnm to about 500 nm.

In several embodiments, the platform unit further comprises a film,wherein the film is configured to block at least one sensor fromgenerating a signal in response to a change in humidity. In someembodiments, the film comprises a resin selected from the groupconsisting of an epoxy resin, a silicon resin, a polyamide resin, apolyimide resin, a poly(p-xylylene) resin and a combination thereof.Each possibility represents a separate embodiment of the presentinvention. In additional embodiments, the film thickness ranges fromabout 1 μm to about 1000 μm.

According to one embodiment, the platform unit further provides thedetection of a volatile organic compound (VOC) of interest using ananalyte sensor, wherein the analyte sensor is configured to sense ananalyte adsorbed thereon and to generate an electrical signal inresponse thereto. In another embodiment, the platform unit furtherprovides the detection of a volatile organic compound indicative of adisease in a subject. In yet another embodiment, the platform unitfurther comprises a film, wherein the film is configured to block atleast one sensor (e.g. the temperature, humidity and/or pressure sensor)from generating a signal in response to a volatile organic compound(VOC) of interest.

In various embodiments, the platform unit comprises at least threesensors comprising metallic nanoparticles capped with similar ordifferent organic coatings, wherein the three sensors comprise apressure sensor being deposited on a substantially flexible substrate,wherein the pressure sensor is configured to sense pressure appliedthereon and to generate an electrical signal in response thereto, atemperature sensor configured to exhibit a change in conformation of themetallic nanoparticles capped with an organic coating in response to achange in temperature and generate an electrical signal in responsethereto, and a humidity sensor configured to exhibit a change inconformation of the metallic nanoparticles capped with an organiccoating in response to a change in humidity and generate an electricalsignal in response thereto.

In one embodiment, the platform unit comprises at least three sensorscomprising metallic nanoparticles capped with similar or differentorganic coating, wherein the three sensors comprise a pressure sensorbeing deposited on a substantially flexible substrate, wherein thepressure sensor is configured to sense pressure applied thereon and togenerate an electrical signal in response thereto, a temperature sensorbeing deposited on a substantially rigid substrate, wherein thetemperature sensor is configured to exhibit a change in conformation ofthe metallic nanoparticles capped with an organic coating in response toa change in temperature and generate an electrical signal in responsethereto, and a humidity sensor being deposited on a substantially rigidsubstrate, wherein the humidity sensor is configured to exhibit a changein conformation of the metallic nanoparticles capped with an organiccoating in response to a change in humidity and generate an electricalsignal in response thereto. In exemplary embodiments, the pressuresensor and the temperature sensor comprise organic coating having lowsensitivity to humidity (i.e. water vapor). In another exemplaryembodiment, the pressure sensor and the temperature sensor comprise afilm which is configured to block the sensors from generating a signalin response to a change in humidity.

In other embodiments, at least one sensor in the platform unit comprisesdual sensing sensitivities. In one exemplary embodiment, the sensorcomprising dual sensing sensitivities is a temperature and humiditysensor being deposited on a substantially flexible or rigid substrate,wherein the sensor is configured to exhibit a change in conformation ofthe metallic nanoparticles capped with an organic coating in response toa change in temperature and a change in humidity and generate aplurality of different electrical signals in response thereto. Inanother exemplary embodiments, the sensor comprising dual sensingsensitivities is a pressure and humidity sensor being deposited on asubstantially flexible substrate, wherein the sensor is configured tosense pressure applied thereon and to generate an electrical signal inresponse thereto and is further configured to exhibit a change inconformation of the metallic nanoparticles capped with an organiccoating in response to a change in humidity and generate an electricalsignal in response thereto. In yet another exemplary embodiment, thesensor comprising dual sensing sensitivities is a pressure andtemperature sensor being deposited on a substantially flexiblesubstrate, wherein the sensor is configured to sense pressure appliedthereon and to generate an electrical signal in response thereto and isfurther configured to exhibit a change in conformation of the metallicnanoparticles capped with an organic coating in response to a change intemperature and generate an electrical signal in response thereto.

In other exemplary embodiments, the platform unit of the presentinvention comprising two sensors, wherein one sensor is a dual pressureand humidity sensor being deposited on a substantially flexiblesubstrate, and the other sensor is a dual pressure and temperaturesensor being deposited on a substantially flexible substrate.

One of skill in the art readily understands that a signal whichcorresponds to changes in each of load, temperature and/or humidity canbe extracted from a dual sensor's signal using various pre-measurementcalibrations and/or post-measurement calculations using algorithms knownby those of skill in the art.

In some embodiments, the humidity sensor comprises continuous anddiscontinuous regions of metallic nanoparticles capped with an organiccoating. In one embodiment, the discontinuous regions comprise voidsranging in size from about 10 nm to about 500 nm. In another embodiment,the discontinuous regions comprise between about 3% and about 90% voids.

According to additional embodiments, the platform unit of the presentinvention is integrated on electronic or artificial skin surface.

Further embodiments and the full scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter. However, it should be understood that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B: (FIG. 1A) ΔR/R_(b) of NTMBT-MCNP-based sensor in responseto changing the temperatures from 23° C. to 39° C. Inset: amagnification of the temperatures region of 35-39° C. (FIG. 1B) ΔR/R_(b)of NTMBT-MCNP-based sensor in response to various relative humiditylevels.

FIG. 2: Relative responses of five duplicated MCNP-based sensors toincrease in relative humidity levels.

FIGS. 3A-3I: (FIG. 3A) A schematic illustration of the relaxed substratewith ETP-MCNPs film. (FIG. 3B) A schematic illustration of the bentsubstrate with ETP-MCNPs film and the effect of the bending on theETP-MCNPs spacing. (FIGS. 3C-3E): Photographs of the device on PET in(FIG. 3C) relaxed state, (FIG. 3D) upward bent, and (FIG. 3E) downwardbent. The distance between the electrodes is about 1 mm. (FIG. 3F)ΔR/R_(b) of ETP-MCNP-based sensor on PET in response to stretchingduring three-point bending measurements with loading (▪) and unloading(◯) of stress. (FIG. 3G) ΔR/R_(b) of ETP-MCNP-based sensor on PET inresponse to compression during three-point bending measurements withloading (▪) and unloading (◯) of stress. The dashed lines representlinear fits to the curves, with R² in the range of 0.996-0.999 for all 4curves. The sensitivity limit is down to tens of Pa, with 40 Pa beingthe limit of detection for the PET substrate. (FIG. 3H) ΔR/R_(b) ofETP-MCNP sensor (thick line) to load and unload (thin line) vs. time.(FIG. 3I) ΔR/R_(b) vs. time in response to 12 cycles of load (0.75 gr)and unload.

FIGS. 4A-4D: ΔR/R_(b) of DT-GNP-based sensor to (FIG. 4A) stretching and(FIG. 4B) compressing the PE substrate by uploading (□) and downloading(●) of stress during three-point bending experiment. The responses arelinear and repeatable. (FIG. 4C) Resistance shifts of the DT-MCNP-basedsensor as a result of bending the surface. The load onset is indicatedin grams. (FIG. 4D) Repeatability of sensor's response to applied stressof ˜250 Pa (˜0.5 gram).

FIGS. 5A-5C: FE-HRSEM images of a layer of ETP-MCNP which was dropcasted on Mylar 36 substrate. (FIG. 5A) An image of the drop marginsusing SE detector; (FIG. 5B) An image of the center of the drop using SEdetector. (FIG. 5C) An image of the center of the drop using BSEdetector. The dashed white circles in (FIGS. 5B and 5C) mark cracks asdeep as the layer-substrate interface.

FIGS. 6A-6G: High magnification FE-HRSEM images of the margins ofETP-MCGNP drop casted layer on (FIG. 6A) Kapton 50, (FIG. 6B) Kapton127, (FIG. 6C) PET 125, (FIG. 6D) Kapton® b. 131, (FIG. 6E) Mylar® 36,(FIG. 6F) Mylar 50 and (FIG. 6G) PVC 200 using SE detector.

FIGS. 7A-7G: FE-HRSEM images of the margins of ETP-MCGNP drop castedlayer on (FIG. 7A) Kapton 50, (FIG. 7B) Kapton® 127, (FIG. 7C) PET 125,(FIG. 7D) Kapton® b. 131, (FIG. 7E) Mylar® 36, (FIG. 7F) Mylar® 50 and(FIG. 7G) PVC 200 using SE detector.

FIGS. 8A-8G: Low magnification FE-HRSEM images of ETP-MCNP drop-castedlayer on: (FIG. 8A) Kapton 50, (FIG. 8B) Kapton® 127, (FIG. 8C) PET 125,(FIG. 8D) Kapton® b. 131, (FIG. 8E) Mylar® 36, (FIG. 8F) Mylar® 50, and(FIG. 8G) PVC 200, using SE detector.

FIGS. 9A-9B: (FIG. 9A) ΔR/R_(b) of ETP-MCNP films on different flexiblesubstrates (Mylar® 50: ♦; Mylar® 36: ∇; PET 125: ◯; Kapton® b. 131: ♦;Kapton® 127: ∇; Kapton® 50: ★; and PVC

) vs. load, as measured by three-point bending tests. (FIG. 9B) The loadsensitivity of the sensors having substrates with different properties,as a function of the Young's modulus, geometrical property, and momentof inertia.

FIGS. 10A-10B: ΔR/R_(b) vs. load (bottom x-axis) and strain (upperx-axis) for: (FIG. 10A) ETP-MCNP film deposited on Mylar® 36 (loadsensitivity=0.31) subjected to loads of 200 mg-1 gr; and (FIG. 10B)ETP-MCNP film deposited on PET 125 (load sensitivity=0.01) subjected toloads of 200 mg-10 gr.

FIGS. 11A-11B: (FIG. 11A) ΔR/R_(b) of ETP-MCNP sensor (thick line) toload and unload (thin line) vs. time. (FIG. 11B) The load sensitivity ofthe sensors produced on substrates with different elastic properties, asa function of the Young's modulus and the substrate thickness. The errorbars are the standard deviation of 3 similar sensors and the dashed linerepresents the linear trend of the results.

FIGS. 12A-12C: (FIG. 12A) The change in load sensitivity (left y-axis)and sensors' resistance (right y-axis) using sensors fabricated onelectrodes with 0.5 mm, 1 mm and 3 mm spacing. The error bars are thestandard deviation of 3 tested sensors for specific electrode spacing.(FIG. 12B) The change in load sensitivity for the same electrodestructure and substrate when changing the width of the substrate. Theerror bars are the standard deviation of 3 repetitions on the samesensor with specific dimensions. (FIG. 12C) The change in loadsensitivity for different MCNP ligands (NTMBT: ◯; and ETP:

). The dashed lines represent linear fits to the curves and the errorbars are standard deviation of 3-5 sensors.

FIG. 13: Gauge Factor (GF) values that were extracted from linear fitsof the sensors' relative response vs. the strain. The asterisksrepresent the results described herein and the circles are GF valuesfrom Farcau et al., ACS Nano 2011, 5, 7137-7143; Tsung-Ching et al., J.Disp. Tech. 2009, 5, 206-215; Vossmeyer et al., Adv. Funct. Mater. 2008,18, 1611-1616; and Herrmann et al., Appl. Phys. Lett. 2007, 91, 183105.The dashed line represents a linear fit.

FIGS. 14A-14B: (FIG. 14A) Change in the baseline resistance ofETP-MCNP/Kapton® 127 sensors vs. the number of bending cycles. (FIG.14B) ΔR/R_(b) vs. load after 1 (∇), 5,000 (Δ), and 10,000 (◯) bendingcycles.

FIGS. 15A-15B: (FIG. 15A) ΔR/R_(b) of ETP-MCNP-based sensor on a PETsubstrate upon changes in temperature from 23° C. to 39° C. Inset: RHfluctuations during the experiment. (FIG. 15B) ΔR/R_(b) ofETP-MCNP-based sensor to various RH levels. The dashed line represents alinear fit with R²=0.98. The error bars are the standard deviations oftens of measurement points of the response at a specific RH level.Inset: Temperature fluctuations during the experiment.

FIGS. 16A-16C: (FIG. 16A) Morse code alphabet and digits. (FIG. 16B)Encoding “LNBD” on ETP-MCNP-based sensor with a 36 μm thick Mylar®substrate. (FIG. 16C) Encoding “SOS” on ETP-MCNP-based sensor with a 125μm thick PET substrate. The piessuie was applied using a finger (with anestimated pressure of approximately 1 KPa).

FIG. 17: A schematic illustration of a prototype platform for sensinghumidity, RH and load using different substrates (PET substrate at thecenter and silicon dioxide substrates at the sides) and 2 differentMCNPs (ETP at the center and NTMBT at the sides). The lines crossing thesubstrates represent metal electrodes.

FIGS. 18A-18D: ΔR/R_(b) of a perforated NTMBT-MCNP sensor on a silicondioxide substrate vs. (FIG. 18A) relative humidity, and (FIG. 18B)temperature. ΔR/R_(b) of ETP-MCNP sensor on a silicon dioxide substratevs. (FIG. 18C) relative humidity, and (FIG. 18D) temperature.

FIGS. 19A-19B: (FIG. 19A) The resistance of flexible ETP-MCNP sensor onPET substrate as a function of the temperature at 3% RH (▴) and at 20%RH (◯). The plots on the right show the RH fluctuations when changingthe temperatures. (FIG. 19B) The resistance of flexible ETP-MCNP sensoron PET substrate as a function of % RH at 21° C. (∇), 25° C. (×) and 30°C. (●). The plots on the right describe the temperature fluctuationswhen changing the RH conditions.

FIG. 20: Calculated planes for an ETP-MCNP sensor on a PET substrate for3 different loads. Load 0: unloaded; Load 1: 3 gr load; and Load 2: 6 grload. The temperature and RH were measured by the inflexible ETP-MCNPand NTMBT-MCNP sensors. The parameters were calculated using solverscript in excel.

FIGS. 21A-21C: (FIG. 21A) A schematic illustration of an exemplaryplatform of the present invention using a Kapton® substrate and goldelectrodes. (FIG. 21B) Different planes representing changes inresistance of S1 and S2 when exposing the sensors to changing conditionsof temperature and relative humidity. (FIG. 21C) ΔR/R_(b) of S3 toapplied pressure.

FIGS. 22A-22B: (FIG. 22A) A schematic illustration of the three-pointbending setup. The points marked by the bottom arrows represent thestatic lean beams on which the flexible substrate rests. The upper arrowrepresents the location at which strain is applied. (FIG. 22B) Aschematic illustration of the stretching setup. The substrate is in a“dog bone” morphology were the grips are attached to the wider part ofthe sample. The arrows represent the direction of the applied strain.

FIG. 23: A schematic illustration of a three-point bending sampledimensions.

FIG. 24: A schematic illustration of the three-point bending setup.Point #1 and point #2 are the static lean beams on which the flexiblesubstrate rests. Point #3 is where the pressure is applied, using adisconnected, screw-controlled probe. The resistance of the MCNP film ismeasured through the drain and source electrodes.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a modular matrix or platform unit for theconcurrent detection of pressure, temperature and humidity. Inparticular, provided herein is a platform comprising MCNP-based sensorswhich operate at low-power (<0.5V) for multi-functional artificial orelectronic skin applications.

The present invention is based in part on the unexpected finding thatMCNP-based flexible sensors can possess repeatable measurements ofelastic deformation with load sensitivity ≦0.24 gr. In addition, it isfurther disclosed that the same sensor technology can be used forsensing environmental conditions with excellent sensitivities formeasuring changes in temperature (below 1° C.) and humidity (below 1%RH). It was not previously realized that it is possible to useMCNP-based sensors for concurrent detection of pressure, temperature andhumidity on a single platform unit. The ability to detect pressure,temperature and humidity using the same sensor technology integrated ona single platform unit provides a significant advantages over the priorart. The MCNP-based sensors provide repeatable responses even after manybending cycles which render them advantageous for long-term use. Anotheradvantage to the present invention stems from the ability to manufacturemicro-scale sensors having high spatial resolution in mass production,thereby enabling their integration in an artificial or electronic skinin well-defined and controllable locations.

In order to achieve independent sensitivities of individual sensors to asingle desirable parameter, the following fabrication modulations can beapplied:

(i) by using substrates having varying flexibilities and geometriccharacteristics. For example, by using substantially flexiblesubstrates, the sensor generates an electrical signal mainly attributedto the applied force and not to changes in temperature and humidity.Similarly, by using substantially rigid non-stretching substrates, thesensor generates an electrical signal mainly attributed to changes intemperature and/or humidity and not to pressure.

(ii) by using different organic coatings of the metallic nanoparticles.For example, by using a short di-thiol linker as the capping organiccoating, the responses of the sensor to gaseous analytes (includingwater vapors) can be substantially suppressed. By using a long linker asthe capping organic coating, adsorption of various gases can be obtainedthereby affording a measurable electrical signal in response to theswelling of the assembly of capped nanoparticles.

(iii) by adding a thin (˜50 μm thick) polymer film, as the top-cover ofthe sensor. For example, the addition of a top cover can substantiallysuppress the sensing of humidity and/or volatile organic compounds.Thus, it is contemplated that a thin top-cover film would restrict watervapors from interacting with the metallic nanoparticles capped with anorganic coating. The top cover should be thin and possess good heatconduction and low heat capacitance characteristics to assure fast andaccurate responses to changes in temperature and/or pressure.

(iv) by modifying the deposition parameters. For example, by using thelayer-by-layer deposition technique (Makishima et al., J. Non-Cryst.Sol. 1973, 12, 35-45), control over sensing sensitivities to variousanalytes can be obtained.

(v) by depositing the NPs at different humidity levels. Thus, it iscontemplated that a sensor comprising a film of MCNP which hasdiscontinuous regions provides positive responses upon exposure tovarious analytes, but negative responses upon exposure to water vapor.By changing the amount of voids in the discontinuous regions, it ispossible to control the sensitivity to humidity (water vapors).

(vi) by using pre-measurement calibrations and/or post-measurementalgorithmic compensation, an extraction of the data affected by a singleparameter (e.g., only temperature) or a plurality of parameters(temperature, humidity and load or strain) can be obtained. For example,two sensors with low sensitivity to load or strain can afford thesensing of changes in temperature and humidity each, while a thirdflexible sensor affords the sensing of temperature, humidity and load orstrain. Post-measurement algorithms can be used to compensate thesignals produced by changes in temperature and humidity of the thirdflexible sensor and enable the extraction or isolation of the signalgenerated by applied load or strain. In another example, two sensors maysense temperature and humidity simultaneously, having differentsensitivities towards each parameter. Then, post-measurement algorithmscan be used to calculate the temperature and the relative humidity in aninjective manner.

The MCNP-based sensing platform unit of the present invention isparticularly suitable for use in artificial or electronic skintechnology. The platform unit of the present invention obviates the needfor complex integration processes of substantially different devices,each device being sensitive to humidity, temperature, or pressure. TheMCNP-based sensing platform unit of the present invention is compatiblewith cost-effective mass production using various deposition techniques(e.g. spray coating). An additional advantage stems from the wide rangeof pressures that can be detected and measured by the pressure sensors,which can be achieved by depositing MCNPs on different substrates havingvarious mechanical properties and geometrical characteristic. Moreover,the use of MCNPs pressure sensors on flexible substrates afforded themeasurement of very low pressures that have never been detected by thehitherto known pressure sensors (Maenosono et al., J. of Nanopart. Res.2003, 5, 5-15). Another advantage of the MCNP-based sensors is theirability to operate at low voltage of ˜0.5V, whereas the hitherto knownskin technologies require operation at 5V or more. Such low voltagedemands facilitate the integration of the technology presented hereinusing mobile batteries.

The present invention therefore provides MCNP-based sensing platformunit with excellent temperature and humidity sensitivities which enablesthe sensing of environmental conditions. The MCNP-based sensing platformunit of the present invention also provides excellent sensitivity tostrain which enables its use as “touch” sensors. The MCNP-based sensingplatform unit can be integrated in artificial or electronic skinapplications.

According to the principles of the present invention, the platform unitprovides the detection of pressure, temperature, and/or humidity. Insome embodiments, the platform unit provides the concurrent detection ofpressure, temperature, and humidity. The platform unit comprises aplurality of sensors, each sensor comprises a plurality of metallicnanoparticles capped with an organic coating. In certain embodiments,each sensor comprises a plurality of metallic nanoparticles capped withdifferent organic coatings. Suitable metallic nanoparticles within thescope of the present invention include, but are not limited to Au, Ag,Ni, Co, Pt, Pd, Cu, Al, and combinations thereof, including metallicalloys such as, but not limited to Au/Ag, Au/Cu, Au/Ag/Cu, Au/Pt, Au/Pd,Au/Ag/Cu/Pd, Pt/Rh, Ni/Co, and Pt/Ni/Fe. Each possibility represents aseparate embodiment of the present invention.

The organic coating of the metallic nanoparticles comprises a monolayeror multilayers of organic molecules. Suitable coating includes, but isnot limited to alkylthiols, e.g., alkylthiols with C₃-C₂₄ chains,arylthiols, alkylarylthiols, alkenyl thiols, alkynyl thiols, cycloalkylthiols, heterocyclyl thiols, heteroaryl thiols, alkylthiolates, alkenylthiolates, alkynyl thiolates, cycloalkyl thiolates, heterocyclylthiolates, heteroaryl thiolates, ω-functionalized alkanethiolates,arenethiolates, (γ-mercaptopropyl)tri-methyloxysilane, dialkyldisulfides and combinations thereof. Each possibility represents aseparate embodiment of the present invention. Exemplary organic coatingincludes, but is not limited to 2-nitro-4-trifluoro-methylbenzenethiol,3-ethoxythiophenol, dodecylamine, and decanethiol. Each possibilityrepresents a separate embodiment of the present invention. In variousembodiments, the organic coating is characterized by a thickness rangingfrom about 1 nm to about 500 nm.

Sensors comprising metallic nanoparticles capped with an organic coatingcan be synthesized as is known in the art, for example using thetwo-phase method (Brust et al., J. Chem. Soc. Chem. Commun., 1994, 7,801) with some modifications (Hostetler et al., Langmuir 1998, 14, 17).In a non-limiting example, AuCl₄ ⁻ is transferred from aqueousHAuCl₄.xH₂O solution to a toluene solution by the phase-transfer reagentTOAB. After isolating the organic phase, excess thiols are added to thesolution. The mole ratio of thiol: HAuCl₄.xH₂O can vary between 1:1 and10:1, depending on the thiol used. This is performed in order to preparemono-disperse solution of gold nanoparticles in an average size of about3-6 nm. Exemplary procedures include, but are not limited to thiol:Aumole ratios of 10:1 and 1:1 for dodecanethiol and butanethiol-cappedgold nanoparticics, respectively at an average size of about 5 nm. Aftervigorous stirring of the solution, aqueous solution of the reducingagent NaBH₄ in large excess is added. The reaction is constantly stirredat room temperature for at least 3 hours to produce a dark brownsolution of the thiol-capped Au nanoparticles. The resulting solution isfurther subjected to solvent removal in a rotary evaporator followed bymultiple washings using ethanol and toluene. Gold nanoparticles cappedwith e.g. 2-mercaptobenzimidazole can be synthesized by theligand-exchange method from pre-prepared hexanethiol-capped goldnanoparticles. In a typical reaction, excess of thiol,2-mercaptobenzimidazole, is added to a solution of hexanethiol-cappedgold nanoparticles in toluene. The solution is kept under constantstirring for a few days in order to allow as much ligand conversion aspossible. The nanoparticles are purified from free-thiol ligands byrepeated extractions. The metallic nanoparticles may have any desirablegeometry including, but not limited to a cubic, a spherical, and aspheroidal geometry. Each possibility represents a separate embodimentof the present invention.

In some embodiments, the plurality of sensors comprise at least onepressure sensor which is configured to sense pressure applied thereonand to generate an electrical signal in response thereto. According tothe principles of the present invention, the pressure sensor isfabricated on a substantially flexible substrate. The term “asubstantially flexible substrate” as used herein refers to a substratewhich is configured to elastically deform in response to pressure,wherein said deformation is proportional to the amount of appliedpressure. In certain embodiments, the deformation of the substrategenerates a change in conformation of the metallic nanoparticles cappedwith an organic coating. The change in conformation or structuraldisplacement of the metallic nanoparticles capped with an organiccoating generates an electrical signal which is proportional to theamount of applied pressure. In other embodiments, the pressure sensor isconfigured as a strain gauge which translates the mechanical deflectioninto an electrical signal.

Suitable substantially flexible substrates include stretchablesubstrates as is known in the art. Exemplary substrates include, but arenot limited to polymers which may be polyimide (e.g. Kapton®),polyamide, polyimine (e.g. polyethylenimine), polyethylene, polyester(e.g. Mylar®, polyethylene terephthalate, polyethylene naphthalate),polydimethylsiloxane, polyvinyl chloride (PVC), polystyrene and thelike. Each possibility represents a separate embodiment of the presentinvention. In one embodiment, the substrate comprises silicon dioxide.In another embodiment, the substrate comprises Si rubber. By modifyingthe material which forms the substantially flexible substrate from amaterial having high Young's modulus to a material having low Young'smodulus, a change in load sensitivities can be obtained. It is thuscontemplated that the substantially flexible substrate enables tocontrol the load sensitivity of the pressure sensor.

The substantially flexible substrate can have any desirable geometry. Inrectangular geometries, the width of the substantially flexiblesubstrate ranges between about 0.01-10 cm. The thickness of thesubstrate can further be tuned, typically in the range of about 20-500μm. The present invention provides the modulation of load sensitivitiesby changing the width of the sensors' substrate. In addition, thepresent invention provides the modulation of the gauge factor byadjusting the substrate thickness. Thus, it is contemplated that bymodifying the geometrical characteristics of the substrate, desirableload sensitivity and strain gauge factor can be obtained.

The platform unit of the present invention further comprises at leastone temperature and/or humidity sensor configured to exhibit a change inconformation of the metallic nanoparticles capped with an organiccoating in response to a change in temperature and/or a change inhumidity. This change in conformation is then translated into anelectrical signal generated in response. Accordingly, the electricalsignal is proportional to the change in humidity and/or change intemperature.

In some embodiments, the temperature and/or humidity sensor isfabricated on a substantially rigid or substantially flexible substrateas described herein. Typically, the temperature and/or humidity sensoris fabricated on a substantially rigid substrate. Suitable substantiallyrigid substrates within the scope of the present invention include, butare not limited to metals, insulators, semiconductors, semimetals, andcombinations thereof. Each possibility represents a separate embodimentof the present invention. In exemplary embodiments, the substantiallyrigid substrate comprises silicon dioxide on a silicon wafer. In anotherexemplary embodiment, the substantially rigid substrate comprises asubstantially rigid polymer. In yet another exemplary embodiment, thesubstantially rigid substrate comprises indium tin oxide.

In various embodiments, the pressure and/or temperature sensors of thepresent invention are coated with a film. According to the principles ofthe present invention, the film is configured to block the pressureand/or temperature sensors from generating a signal in response to achange in humidity. Non-limiting examples of films within the scope ofthe present invention include epoxy resin films, silicon resin films,polyamide resin films (e.g. nylon and aramid resins), polyimide resinfilms, poly(p-xylylene) resin films (e.g. Parylenes®) and a combinationthereof. Each possibility represents a separate embodiment of thepresent invention. Typically, the film which is configured to block thepressure and/or temperature sensors from generating a signal in responseto a change in humidity has thickness in the range of about 1-1000 μm.

According to certain aspects and embodiments, the platform unitcomprises at least three sensors comprising metallic nanoparticlescapped with an organic coating as follows:

(i) a pressure sensor being deposited on a substantially flexiblesubstrate, wherein the pressure sensor is configured to sense pressureapplied thereon and to generate an electrical signal in responsethereto;

(ii) a temperature sensor being deposited on a substantially rigidsubstrate, wherein the temperature sensor is configured to exhibit achange in conformation of the metallic nanoparticles capped with anorganic coating in response to a change in temperature and generate anelectrical signal in response thereto; and

(iii) a humidity sensor being deposited on a substantially rigidsubstrate, wherein the humidity sensor is configured to exhibit a changein conformation of the metallic nanoparticles capped with an organiccoating in response to a change in humidity and generate an electricalsignal in response thereto.

In some embodiments, the temperature and humidity sensors are configuredto exhibit an independent change in conformation of the metallicnanoparticles capped with an organic coating in response to each of achange in temperature or a change in humidity.

According to certain aspects and embodiments, the humidity sensorcomprises continuous and discontinuous regions of conductive metallicnanoparticles capped with an organic coating. In one embodiment, thediscontinuous regions comprise voids ranging in size from about 10 nm toabout 500 nm, wherein the percentage of voids ranges between about 3%and about 90%.

In certain embodiments, the platform unit comprises a plurality ofconducting elements (e.g. electrodes) which are coupled to each sensor,thereby enabling the measurement of the signals generated by thesensors. The conducting elements may include a source and a drainelectrode separated from one another by a source-drain gap. Theconducting elements may further comprise a gate electrode wherein theelectrical signal may be indicative of a certain property of the cappednanoparticles (e.g. a change in conformation of the cappednanoparticles) under the influence of a gate voltage.

The conducing elements may comprise metals such as Au, Ag or Ptelectrodes and may further be connected by interconnecting wiring. Thedistance between adjacent electrodes defines the sensing area.Accordingly, different configurations of the electrodes in the platformunit may be fabricated as is known in the art. Typically, the distancebetween adjacent electrodes in each sensor ranges between about 0.01-5mm. In some embodiments, the metallic nanoparticles are casted on aplurality of interdigitated electrodes on a substantially flexible orrigid substrate.

The electrical signal which is generated by the pressure, temperature orhumidity sensors may comprise, according to the principles of thepresent invention any one or more of conductivity, resistance,impedance, capacitance, inductance, or optical properties of thesensors. In some embodiments, the electrical signal is produced by theswelling of the assembly of capped nanoparticles in response to changesin pressure, temperature or humidity. As used herein, the term“swelling” refers to an increase of the average inter-particle distancein the assembly of capped nanoparticles. In other embodiments, theelectrical signal is produced by the aggregation of the assembly ofcapped nanoparticles in response to changes in pressure, temperature orhumidity. As used herein, the term “aggregation” refers to a decrease ofthe average inter-particle distance m the assembly of cappednanoparticles.

The sensor signal can be detected by a detection means. Suitabledetection means include devices which are susceptible to a change in anyone or more of resistance, conductance, alternating current (AC),frequency, capacitance, impedance, inductance, mobility, electricalpotential, optical property and voltage threshold. Each possibilityrepresents a separate embodiment of the present invention. In additionalembodiments, the detection means includes devices which are susceptibleto swelling or aggregation of capped nanoparticles as well as deviceswhich are susceptible to a change in any one or more of optical signal(detected by e.g. spectroscopic ellipsometry), florescence,chemiluminsence, photophorescence, bending, surface acoustic wave,piezoelectricity and the like. Each possibility represents a separateembodiment of the present invention. The measured electrical signals canbe displayed on a display or transmitted to a host computer.

The sensors of the present invention can be configured as any one of thevarious types of electronic devices, including, but not limited tocapacitive sensors, resistive sensors, chemiresistive sensors, impedancesensors, field effect transistor sensors, and the like, or combinationsthereof. Each possibility represents a separate embodiment of thepresent invention. In a non-limiting example, the sensors of the presentinvention are configured as chemiresistive sensors (i.e.chemiresistors). In one embodiment, the sensors of the present inventionare not configured as impedance sensors.

Sensors comprising a plurality of metallic nanoparticles capped with anorganic coating can be formed on flexible or rigid substrates using avariety of techniques well known in the art. Exemplary techniquesinclude, but are not limited to,

(i) Random deposition from solution by drop casting, spin coating, spraycoating and other similar techniques. Each possibility represents aseparate embodiment of the present invention.

(ii) Field-enhanced or molecular-interaction-induced deposition fromsolution. Each possibility represents a separate embodiment of thepresent invention.

(iii) Langmuir-Blodgett or Langmuir-Schaefer techniques. Eachpossibility represents a separate embodiment of the present invention.

(iv) Soft lithographic techniques, such as micro-contact printing (mCP),replica molding, micro-molding in capillaries (MIMIC), andmicro-transfer molding (mTM). Each possibility represents a separateembodiment of the present invention.

(v) Various combinations of Langmuir-Blodgett or Langmuir-Schaefermethods with soft lithographic techniques. Each possibility represents aseparate embodiment of the present invention.

(vi) Printing on solid-state or flexible substrates using an injectprinter designated for printed electronics.

The present invention further encompasses sensors having dual sensingsensitivities, such as a dual temperature and pressure sensor, a dualtemperature and humidity sensor, and/or a dual pressure and humiditysensor. Each possibility represents a separate embodiment of the presentinvention.

A non-limiting example of a platform unit which comprises dual sensorsincludes a platform unit comprising three sensors, wherein two sensorsare dual temperature and humidity sensors being deposited on asubstantially flexible substrate, and a third pressure sensor beingdeposited on a substantially flexible substrate. It is contemplated thatthe choice of substrate is used to alter the sensitivity of the sensorsto changes in load, temperature and/or humidity. An additionalnon-limiting example of a platform unit which comprises dual sensorsincludes a platform unit comprising two sensors, wherein one sensor is adual pressure and humidity sensor being deposited on a substantiallyflexible substrate, and the other sensor is a pressure and temperaturesensor being deposited on a substantially flexible substrate. One ofskill in the art readily understands that a signal generated by eachparameter (temperature, humidity or pressure) is extracted usingpre-measurement calibration, post-measurement calculation or acombination thereof.

The arrangement of the plurality of sensors in the platform unit can beperformed as is known in the art. Non-limiting arrangement includes amatrix of sensors (rows and columns) comprising a plurality of sensors,for example between 2 and 20 sensors, wherein each sensor independentlygenerates an electrical signal in response to pressure, temperatureand/or humidity. Each sensor comprises metallic nanoparticles cappedwith a different or similar organic coating and a different or similarsubstrate.

According to certain aspects and embodiments, the sensors of the presentinvention are coated with a film. In some embodiments, the film providesthe protection of the metallic nanoparticles capped with an organiccoating from physical damage, scratching and oxidation. The coating canbe performed by processes well known in the art such as, but not limitedto, spin coating and the like. The film could be permeable to water ornot, depending on the required application. The film could conduct heator isolate the sensor from external temperature changes. In someembodiments, the film comprises polycyclic aromatic hydrocarbons (PAHs).In other embodiments, the film comprises carbon coatings, nitrogenatedcarbon coatings, thermoplastic resins, silicate coatings or any othersuitable coating known in the art. Typically, the film possesses athickness which ranges from about 0.001 to about 10 μm.

According to various aspects and embodiments, the platform unit furtherprovides the detection of a volatile organic compound (an analyte) usingan analyte sensor, wherein the analyte sensor is configured to sense ananalyte adsorbed thereon and to generate an electrical signal inresponse thereto. Thus, it is contemplated that the platform unit wouldfurther provide the detection of the presence and concentration ofvolatile organic compounds in the surrounding environment. In someembodiments, the volatile organic compounds are biomarkers indicative ofa disease or disorder in a subject.

The platform unit of the present invention may be used for artificialand/or electronic skin applications which require the production oflarge-scale sensor arrays that can sense load, relative humidity andtemperature with high resolution and short response times. Artificialand/or electronic skin may be integrated in medical prosthesis androbotics industries. Additional applications include, but are notlimited to, use by individuals in order to keep track of loads theycarry (e.g. harbor employees) and measure their physical responseincluding body temperature and humidity; and use to cover engines ofcars and planes which can be configured to set alarms once excesstemperature or pressure are being detected and/or early formation ofcracks initiates.

As used herein and in the appended claims the singular forms “a”, “an,”and “the” include plural references unless the content clearly dictatesotherwise. Thus, for example, reference to “an organic coating” includesa plurality of such organic coatings and equivalents thereof known tothose skilled in the art, and so forth. It should be noted that the term“and” or the term “or” is generally employed in its sense including“and/or” unless the content clearly dictates otherwise.

The following examples are presented in order to more fully illustratesome embodiments of the invention. They should, in no way be construed,however, as limiting the broad scope of the invention. One skilled inthe art can readily devise many variations and modifications of theprinciples disclosed herein without departing from the scope of theinvention.

EXAMPLES

Materials and Methods

Synthesis of MCNPs:

Gold (III) chloride trihydrate (HAuCl₄.3H₂O), tetraoctylammonium bromide(TOAB), sodium borohydride, 3-ethoxythiophenol (ETP), decanethiol (DT)and 2-nitro-4-trifluoro-methylbenzenethiol (NTMBT) were purchased fromSigma-Aldrich. All reagents were of analytical grade and were used asreceived. Spherical gold nanoparticles (AuNPs; 3-6 nm in diameter) weresynthesized as described in Peng et al., Nature Nanotech. 2009, 4,669-673; and Dovgolevsky et al., J. Phys. Chem. C. 2010, 114,14042-14049; the content of each of which is hereby incorporated in itsentirety. Briefly, a solution of HAuCl₄ was added to a stirred solutionof TOAB in toluene. After 10 min stirring, the lower aqueous phase wasremoved. Organic ligands and sodium borohydride were subsequently addedto the toluene phase. After 3 hours at ice temperature, the loweraqueous phase was removed and the toluene phase was subsequentlyevaporated by rotary evaporation. After first washing with cold ethanol,the solution was kept at 5° C. for 18 hours until complete immersion wasachieved. The dark brown precipitate was filtered off and washed withethanol.

Sensor Fabrication:

Electrodes were deposited on different isolating substrates (Table 1).The electrodes were prepared using silver paste (Mouser Electronics).The spacing between the electrodes was typically 1 mm in all experimentsthat examined the substrate effect on the load sensitivity. Similarprinted electrodes with variable spacing of 0.5, 1 and 3 mm were used inorder to examine the effect of spacing between the electrodes.Stretching was performed on “dog bone” samples cut from the samesubstrate as in the bending experiments. Electrodes were prepared in asimilar manner using silver paste with 1 mm spacing between theelectrodes. The substrates were obtained from DuPont (GADOT asdistributers). Flexible sensors were prepared by casting 2 μl of MCNPsin solution on top of the flexible substrates/electrodes.

Morphology Characterization of the MCNP Layers:

The microstructure and morphology of the MCNP films were characterizedby field emission high-resolution scanning electron microscopy (CarlZeiss Ultra Plus FE-HRSEM). The FE-HRSEM analysis was performed usingtwo main detectors: secondary electrons (SE) detector and back scatteredelectrons (BSE) detector. The SE detector provides high-resolutionimaging of the surface. The BSE detector provides image contrast as afunction of elemental composition as well as surface topography.

The morphology of the MCNP films was additionally examined by a tappingmode atomic force microscope (AFM) (Dimension 3100 with Nanoscope IIIacontroller, Veeco Instruments Inc.) that is equipped with a 100×100 μm²scanner. Silicon cantilevers with a normal resonance frequency of 160kHz and spring constants of 5 N/m (NSCl₄/AlBs, MikroMasch, Estonia) wereused. All images were captured with a scan rate of 1-2 Hz and a pixelresolution of 512×512.

The Set-Up of Bending Experiments:

A MARK 10 ESM301 motorized test stand was used to apply a constantstrain of 1.5 mm/sec. For bending setup (FIG. 22A), the stress wasapplied by an upper beam which is indicated by the upper arrow, and thelower beams were used as supporting beams. Under appliedstress/pressure/force, the substrate was bent. The outer (upper) surfacewas then subjected to compression, while the inner (lower) surface wassubjected to dilatation. The forces were measured by Advanced DigitalFORCE GAUGE, made by Mark10 USA.

The Set-Up of Stretching Experiments:

Strain/force was applied between 2 metal grips on a “dog bone” samplethat is illustrated in FIG. 22B. The arrows represent the direction ofstretching. A MARK 10 ESM301 motorized test stand was used to apply aconstant strain of 1.5 mm/sec between metal grips that were attached tothe wider part of the sample, while most of the strain occurred in thethinner part of the sample. The forces were measured by Advanced DigitalFORCE GAUGE, made by Mark10 USA.

Preparation of the Integrated Pressure/Temperature/Humidity Sensors:

Humidity or temperature sensors based on MCNP layers on SiO₂ substratewere prepared by drop casting aliquots of MCNP solution oninterdigitated electrodes consisting of 24 pairs of Au electrodes (5 μmwidth and 25 μm spacing between adjacent electrodes) on a silicon waferwith a 1000 nm SiO₂ film. Between those sensors, a flexible ETP-MCNPlayer on PET substrate was placed (FIG. 17). The electrodes on the PETwere mash printed by CPC Hi Technologies Ltd. with spacing of 1 mm.

The Set-Up of Evaluation of Temperature and Relative Humidity SensingExperiments:

Twenty sensors were mounted on a custom PTFE circuit board. The boardwas mounted into a stainless steel test chamber with a volume of lessthan 300 cm³. For controlling the relative humidity levels (5-60% RH),purified dry nitrogen (99.9999%) from a commercial nitrogen generator(N-30, On Site Gas Systems, USA) equipped with a nitrogen purifier wasused as a carrier gas. The dry nitrogen was mixed with humidified airgenerated by the system's humidifier module. Controlled temperatureswere produced by a custom-made temperature controller. The sensingexperiments were performed by monitoring the response of the MCNP andenvironmental sensors (RH, temperature) to different relative humidityand temperature levels generated by the system.

During ambient sensing experiments (Tables 3-4 and FIG. 20), monitoringof the response of the MCNP and environmental sensors (RH, temperatureand force gauge sensors) to different relative humidity and temperaturelevels in a room while using an applied force on the tested sensor wasperformed. A Keithleydatalogger device (model 2701 DMM) controlled by acustom Labview program was used to sequentially acquire resistancereadings from the sensor array and voltage readings from theenvironmental sensors.

MCNP-Based Pressure Sensor:

The sensors were prepared on polyethylene (PE) substrates. Ten pairs of4.5 mm wide, interdigitated (ID) electrodes with an inter-electrodespacing of 100 μm were formed on the substrates by evaporation of 20nm/200 nm Ti/Au layer through a shadow mask. Chemiresistors wereprepared by drop casting aliquots of representative MCNP solutions. Ahomemade three-point bending system was used in a probe station. Underapplied force, the beam that is subjected to the three-point bendingtest is bent downwards as schematically illustrated in FIG. 24. Theouter (upper) surface is then subjected to compression; while the inner(lower) surface is under strain. The stress (or compression) can becalculated from the measured deflection of the sample, according to theequations below:

The moment of inertia (I) for a rectangular sample (FIG. 23):

$I = {\frac{b \cdot h^{3}}{12} = {{1.3 \cdot 10^{- 3}}\mspace{14mu} m\; m^{4}}}$

The surface area (A):

A=20 mm²

The applied pressure (P):

$P = \frac{48{EI}\;\delta}{L^{3}}$

Where E is the Young's modulus and δ is the deflection of the center ofthe sample. For example, when using polyethylene as a substrate,δ_(minimum)=0.075 mm, the Young's modulus is 500 MPa, and the pressurefor each deflection value:P=0.032·δ

Using the minimal measured deflection value of 0.075 mm, the sensor wassubjected to a load of 0.24 gr:P(δ=0.075 mm)=2.4·10⁻³ N=0.24 gr

and the resulting calculated stress (σ) is:

$\sigma = {\frac{P}{A} = {{{1.2 \cdot 10^{- 4}}\mspace{14mu}{MPa}} = {0.12\mspace{14mu}{KPa}}}}$

The probe station, connected to a device analyzer (Agilent B1500A), wasused to collect the electrical signals of the MCNP-based pressure sensorduring bending and stretching. Resistance as a function of time wasmeasured under constant voltage of 0.5V.

Example 1: Sensing Temperatures and Humidity

The possibility to integrate temperature and humidity sensingcapabilities within the MCNP-based touch platforms was examined. Forthis purpose, nitro-4-trifluoro-methylbenzenethiol (NTMBT) MCNP sensorswere placed in a vacuum chamber with a controllable environment. Thetemperature or relative humidity (RH) was altered in a stepwise manner,and the corresponding ΔR/R_(b) was monitored. FIG. 1A presents theΔR/R_(b) of the sensor upon elevation of the temperature. ΔR/R_(b) waslinear and decreased by 1% with each 1.33° C. increase in thetemperature, making this sensor sensitive enough to monitor thefluctuations of the temperature in the surrounding environment. A zoominto the temperature regime of 35-39° C. shows that the sensitivity ofthe NTMBT-MCNP-based sensor is high enough to act as a human bodythermometer able to precisely detect fluctuations as small as 1° C. orthe presence of a heat source in the vicinity of the artificial orelectronic skin, without the need for touching the object. The abilityof the sensors to sense temperature was further demonstrated using NPsfilms deposited on several slides, including Kapton® 200 μm thick and aPVC slide having a much larger thickness. All devices exhibited a verystrong response to ambient temperature changes: baseline resistanceshifts of 1% as a response to 1° C. change in temperature. Next, 4devices were manufactured on the same Kapton® slide, and connected to aresistance-measurement device. All four resistance values wererepeatedly measured with a cycle time of ˜1 sec. The devices were placedface down on a non-flexible platform. Once a hot object (human hand) wasbrought to the proximity of each (or all) sensor, the baselineresistance changed towards lower values. This phenomenon was repeatedwhenever the hot object was close (1-5 cm) to the device. This effectwas reversible upon removal of the hot object and was not observed whenthe object was at the same temperature as the sensor. The response timesof the sensors were approximated at about 1 sec, namely a significantshift in the baseline resistance approximately 1 second after a humanhand was placed in the proximity of the sensors was observed. Within 15seconds, the resistance had changed by ˜4-6% for all 4 sensors. Thus,the sensors and platform unit of the present invention are verysensitive to temperature and heat and can sense a hot object brought totheir vicinity in a short period of time. The temperature differencebetween the devices' temperature and the human hand brought to itsvicinity was ˜15° C.

FIG. 1B shows the relative responses of a NTMBT MCNP-based sensor in ahumidity region that exists in most environmental applications (5-60%RH). The magnitude of the relative response is linearly proportional tothe measured RH levels, with a sensitivity that is down to a singlepercent RH. Duplicated sensors exhibited good agreement in response todifferent levels of RH (FIG. 2). Specifically, 5 duplicates of thehumidity sensors were tested to evaluate the reproducibility ofproduction and performance. All 5 duplicated MCNP-based sensorsexhibited essentially the same response magnitudes to all tested RHlevels, with a linear dependence on the RH level. These resultsemphasize the possibility of producing and integrating temperature andhumidity sensors as part of an artificial or electronic skin applicationbased on sensors of NTMBT MCNPs.

Example 2: The Effect of Stretching and Bending on the Flexible MCNPSensors

Pressure sensors of gold nanoparticles capped with 3-ethoxythiophenolligands (ETP-MCNP) on flexible polyethylene terephthalate (PET)substrates were examined by a three-point bending test, under bendingand stretching conditions. All experiments were performed at the roomtemperatures of 20° C.±1° C. and relative humidity (RH) levels of50%±3%. FIGS. 3F-3G present load and unload curves of the ETP-MCNPsstrain sensor on PET substrate. The relative resistance responses(ΔR/R_(b), where R_(b) is the baseline resistance with no load appliedon the sensor, and ΔR is the change in resistance between R_(b) and theresistance when load is applied on the sensor) were obtained when theETP-MCNP films were stretched in one case and compressed in the othercase. The positive or negative changes in resistance were linear upongradual change of the bending level of the PET substrate. When theETP-MCNP film was placed on the top side of the PET substrate, bendingthe substrate resulted in a compression of the ETP-MCNP film therebybringing the ETP-MCGNPs closer to each other and allowing highertunneling currents. Accordingly, a decrease in measured resistance wasobtained (FIGS. 3E and 3G). When the ETP-GNPs film was placed on thebottom side of the PET substrate, bending the substrate increased thedistance between the adjacent ETP-GNPs, resulting in a smaller tunnelingcurrent and, therefore, an increase in measured resistance (FIGS. 3D and3F). FIG. 3H shows the ETP-MCNP sensor responses upon continuouscompression with time. Load and unload are represented by a thick lineand load change is represented by a thin line. The sensors responseclosely follows the load curve. The maximum load is about 6 gr and thecorresponding response is ˜20%. In addition, the baseline resistance ofthe sensor after the load-unload cycle is similar. FIG. 3I shows thehigh repeatability of the response of the ETP-MCNP sensor to stretchingwhen subjected to 12 cycles of load (0.75 gr) and unload. As seen in thefigure, the change in the relative resistance response to the load isabout 5%. The sensor's response is repeatable with 1.5% relativestandard deviation of the response (5%±0.075%) and ˜2% relative standarddeviation of baseline resistance values. The load units are presented ingrams wherein a load of lgr is comparable to approximately 0.01N.

Similar results were obtained using gold nanoparticles capped withdecanethiol (DT-MCNP) on flexible polyethylene (PE) substrate. The DTMCNP film was subjected to bending and stretching. FIGS. 4A-4B presentload and unload curves of the DT-MCNPs strain sensor on polyethylene(PE) substrate, subjected to a three-point bending test. The relativeresistance sensing signals (ΔR/R_(b)) show linear positive or negativechanges in resistance upon gradual decrease or increase of the bendinglevel of the PE substrate. When the DT-MCNP film was placed on the PE'stop side, bending the substrate compressed the DT-MCNP film thusdecreasing the distance between adjacent DT-MCNPs, thereby allowinghigher tunneling currents and a decrease in measured resistance (FIG.4B). When the DT-MCNP film was placed on the PE's bottom side, bendingthe substrate increased the distance between adjacent DT-MCNPs,resulting in a smaller tunneling current and, therefore, increasedmeasured resistance (FIG. 4A). There is a significant hysteresis betweenthe load and the unload curves in FIG. 4A. The sensitivity limit is downto tens of Pa, with 20 Pa being the limit of detection for this specificsubstrate. In the current setup, 20 Pa equals to ˜400 mg placed on anarea of 20 mm². As seen in FIG. 4C, by applying loading steps of about0.24 gr, a change in resistance of more than 1 KΩ was obtained. Thenoise was reduced as the weight loaded on the sensor increased. However,weight loads as low as a quarter of a gram were easily detected abovethe noise level. Stretching of the same sensor resulted in similar loadinset, but with positive shifts in the resistance. FIG. 4D shows therepeatability of the response when cycles of load and unload of repeatedstress of 250 Pa on the DT-MCNP sensor were performed. The calculatedsignal-to-noise ratio of the response was about 38, with response timesless than 1 second.

To estimate the range of load sensitivities, similar measurements wereperformed on several substrates with different elastic properties.Three-point bending calculations were performed on several substrateswith different elastic properties (different Young modulus) as follows:PDMS (Young's modulus of 360-870 KPa; PE (Young's modulus of ˜500 MPa);SiO₂ (glass; Young's modulus of ˜70 GPa); and Si rubber (Young's modulusof ˜75 KPa). For minimal load estimation, using the lowest measureddeflection value of 0.075 mm, the sensor was subjected to a load of 0.24gr on a PE substrate. To achieve the same level of deflection (thedeflection is proportional to the strain and the change of resistance)when using PDMS as a substrate under the same experimental conditions,the sensor would have to be subjected to a load of only 0.24 mg and thusa lower detection limit would be achieved. When using glass as thesubstrate, measuring of higher values of stress compared to a PEsubstrate while maintaining similar strain levels can be obtained.Hence, using a deflection value of 0.525 mm, a DT-MCNP-SiO₂ platformwould need to be subjected to a load of 238 gr to achieve similardeflection to that achieved when the DT-MCNP-PE platform was subjectedto a load of 1.7 gr.

When using PDMS as a substrate, the sensor was sensitive to a load of0.24 mg. DT-MCNP on glass (SiO₂) provided sensitivities of higher loads(238 gr) than the sensitivities obtained for DT-MCNP on PE (1.7 gr).When Si rubber was used as the substrate (DT-MCNP-Si rubber platform),the calculated limit of detection was lower by eight-fold in comparisonto the DT MCNP PE platform.

A tunable load sensor based on ETP-MCNP layer casted on a flexiblesubstrate is presented. The low standard deviations and the highsignal-to-noise ratios of the signal's output for repeated load in FIG.3I, assure repeatable measurements of the sensors. When bendingincreases the distance between the nanoparticles, there is an offsetbetween the load and unload sensing curves. Without being bound by anytheory or mechanism of action, this offset can be attributed toirreversible changes in the ETP-MCNP layer (e.g. the formation ofcracks; Olichwer et al., ACS Appl. Mater. Interf. 2012, 4, 6151-6161) orMCNP displacement.

Example 3: The Effect of the Substrate on the MCNP Layer Morphology andon the Related Sensing Properties

The relative response of the sensors is directly proportional to thedeflection (for a certain bending set-up). Accordingly, when introducinglarger deflections, the responses of the flexible sensors increase.Since large deflections can cause irreversible changes both to theflexible substrate as well as to the MCNP layer, a range of loadsensitivities is required. In this manner, high loads are measurableusing thick substrates having high Young's modulus and small loads aremeasurable using thin substrates having low Young's modulus.

The relation between the properties of the substrate and the MCNP-basedload sensors was explored by deposition of ETP-MCNP films on: (i)substrates having similar composition (e.g., the same polymer) butdifferent thicknesses; and (ii) substrates having different compositions(e.g., different polymers) but similar thicknesses (e.g., 50 μm thicksubstrates). The flexible substrates and their properties are listed inTable 1.

TABLE 1 Fabricated MCNP/substrate sensors Young's Substrate modulusthickness Load Substrate (MPa) (μm) Sensitivity^((a)) PVC 200 2200 2000.04 ± 0.003 Kapton ® 50 2500 50 0.23 ± 0.03 Kapton ® 127 2500 127 0.04± 0.014 Kapton ® b. 131 4430 131 0.03 ± 0.008 PET 125 4200 125 0.01 ±0.005 Mylar ® 36 4100 36 0.31 ± 0.036 Mylar ® 50 4100 50 0.07 ± 0.019^((a))load sensitivity: relative change of resistance per unit change inthe load.

The surface morphology of ETP-MCNP films on different substrates wasstudied by field emission high-resolution scanning electron microscopy(FE-HRSEM) and atomic force microscopy (AFM). FIGS. 5A-5C show thesurface morphology of ETP-MCNP film on Mylar® 36. FIG. 5A shows thefilm's margins at low magnification (×200). The layers were deposited bydrop-casting the GNP solution onto the substrates. Cracked “coffeering”-like surface structures, several hundreds of microns in diameter,which were formed during the deposition process are seen. At the centerof the drop (left side of FIG. 5A and FIGS. 5B-5C) a continuous film wasformed. The layer thickness varied between 400 and 900 nm at the centerof the drop (as estimated by AFM measurements). A higher magnification(×30,000) of the center revealed small “bubble-like” structures, part ofwhich having cracked centers (FIGS. 5B-5C). Examining those cracks withback scattered electrons (BSE) analysis (FIG. 5C) showed darker color ascompared to other regions on the ETP-MCNP film, implying that the crackswhich are tens of nanometers deep, expose the layer substrate interface.FIGS. 6A 6G show the ETP-GNP layer margins (which are characterized bythe drop “coffee ring”-like surface structures) of (FIG. 6A) Kapton® 50,(FIG. 6B) Kapton® 127, (FIG. 6C) PET 125, (FIG. 6D) Kapton® b. 131,(FIG. 6E) Mylar® 36, (FIG. 6F) Mylar® 50 and (FIG. 6G) PVC 200. The highmagnification (×30,000) of these figures reveals deep cracks that reachthe polymer substrates. These cracks result in non-conductance of thelayer margins. Images taken at lower magnification show that thisphenomenon is widespread and occurs for a variety of substrates (FIGS.7A-7G).

FIGS. 8A-8G show the center of a deposited drop of ETP-MCNP on varioussubstrates. Similar surface morphology of the ETP-MCNP layers on thedifferent substrates exists. Excluding PVC 200, all substrates exhibitedhighly continuous films, with different substrates resulting indifferent density of the “bubble-like” structures. For PVC 200, cracksappeared over the entire layer. Nevertheless, continuous surface areaswere observed (FIG. 8G). Without being bound by any theory or mechanismof action, the morphology of the “coffee ring” and “bubbles” in theinner part of the layer can be explained by the capillary flow in dropsupon drying (Deegan et al., Nature 1997, 389, 827-828; Deegan et al.,Phys. Rev. E 2000, 62, 756-765; and Deegan, Phys. Rev. E 2000, 6,475-485). The difference in the “bubble” density might be attributed tothe different adhesion between the ETP-MCNP solutions and the differentsubstrates, which, in turn leads to different capillary forces duringthe drying process of the drop. The similar morphology obtained for mostsubstrates used assures that the comparison between ETP-MCNP layers ondifferent substrates is mainly affected by the substrate and not by themorphology differences of the ETP-MCNP layer.

FIG. 9A shows the response of the pressure sensors as measured bythree-point bending tests. All experiments were performed whilemaintaining room temperature at 20° C.±1° C. and relative humidity levelat 50%±3%. The electrical measurements were performed using silverelectrodes with 1 mm spacing between the electrodes. The sensors weretested under a series of loads (0.5-3.5 gr) and the average responses(ΔR/R_(b)) were calculated from 3-5 duplicates. The response increasedlinearly with increasing the load (FIG. 9A). FIG. 9B shows the loadsensitivity of the sensors having substrates with different properties,as a function of the Young's modulus, geometrical property, and momentof inertia. The slope indicates that the load sensitivity depends on thesubstrates' mechanical and geometrical properties. Applying a specificload on different substrates that are coated with similar ETP-MCNPlayers exhibited noticeable differences in the response. For example,applying a load that is equal to 0.9 gr on Kapton® b. 131 coated with aETP-MCNP film, yielded a lower response (˜3%) than the response obtainedusing Mylar® 36 as a substrate that is coated with a similar ETP-MCNPfilm (˜27%). This difference could be attributed to the largerelasticity of the Mylar® 36 substrate. Without being bound by any theoryor mechanism of action, the larger elasticity of the Mylar® 36 substratemay lead to a larger separation between the ETP-MCNPs of the sensinglayer (when the ETP-MCNPs film is at the bottom side of the substrate;Alvares et al., Procedia Eng. 2011, 25, 1349-1352). The slope of therelative resistance versus the load provides the sensor's loadsensitivity, which depends on the Young's modulus, E, and on the momentof inertia, I as follows:

$I = \frac{{bh}^{3}}{12}$

where b is the substrate's width (which was substantially similar in allsubstrates used) and h is the substrate's thickness. The relationbetween the sensor's sensitivity, load, and the substrate parameters isprovided by the following equation:

$\frac{\frac{\Delta\; R}{R_{b}}}{\Delta\; P} \propto \frac{1}{EI}$

where ΔP is the load change. FIG. 9B shows the average loadsensitivities of the substrates as a function of their Young's modulusand the moment of inertia. The load sensitivity clearly depends on thesubstrate properties. Specifically, there is a correlation between thethickness of the substrate and its Young's modulus and the loadsensitivity where thinner substrates having lower Young's moduluspossess higher load sensitivity. The error bars in FIG. 9B represent thestandard deviation of 3-5 similar substrates. For most substrates, thestandard deviation is one order of magnitude smaller than the loadsensitivity mean value.

To estimate the range of the load sensitivities, two types of sensorswere examined under various loads: (i) an ETP-MCNP film deposited onMylar® 36 (load sensitivity=0.31) subjected to 200 mg-1 gr loads; and(ii) an ETP-MCNP film deposited on PET 125 (load sensitivity=0.01)subjected to 200 mg-10 gr loads. FIGS. 10A-10B show the ΔR/R_(b) versusthe load (bottom x-axis) and the strain (upper x-axis). By changing thesubstrate's type, a change in the sensor's response to a specific loadand strain is obtained. When a high response to low strains and loads isrequired, a sensor having high load sensitivity, e.g. Mylar® 36 that has˜15% response to 1 gr load and 0.07% strain (FIG. 10A), can be used.When higher strains and load range are applied, a sensor having smallerload sensitivity, e.g. PET 125 that can sense up to 10 gr load and 0.25%strain (FIG. 10B), can be used.

Stretching properties of the ETP-MCNP-based sensors were tested. “Dogbone” samples (FIG. 11A; inset) were prepared and stretched in “Mark 10”motorized test stand while measuring the force in a complementary forcegauge. Stretching a sample, while applying forces in the substrate'slinear elastic regime of the stress-strain curve, follows the Hocks law:σ=∈E

where σ is the applied force divided by the cross sectional area, S isthe strain in the sample and E is the Young's modulus. In this setup,the width of all of the sensors was substantially equal. Therefore, theload sensitivity is expressed by:

$\frac{\frac{\Delta\; R}{R_{b}}}{\Delta\; P} \propto \frac{1}{Eh}$

where h is the substrate thickness. FIG. 11A shows the ETP-MCNP sensorresponse (thick line) upon continuous stretching load and unload (thinline) with time. The sensor's response closely followed the load curve.The maximum load was about 150 gr with a ˜27% corresponding response.The baseline resistance of the sensor after the load-unload cycle wassimilar. FIG. 11B presents the load sensitivity as a function of thesubstrate's Young's modulus and thickness. The error bars are thestandard deviation of 3 similar sensors. There load sensitivity clearlydepends on the properties of the substrate. For stretching, the appliedforces are significantly larger and the load sensitivities are smaller.

Hence, there is a direct link between the substrate's properties and themeasured load sensitivities, both in bending setup (FIGS. 9A-9B) and instretching setup (FIGS. 11A-11B). The non-linearity can be attributed todifferent adhesion between the ETP-MCNP film and the various substrates.It is, however, evident that the load sensitivity can be modulated bycontrolling the properties of the substrate, using the same MCNPligands. This obviates the need for extensive and expensive synthesisprocedures for producing different MCNPs to achieve a desired sensingfunctionality.

Example 4: Fine Tuning of the Sensing Properties of the Flexible MCNPSensors

For determining the factors which control the load sensitivity of thesensors, additional parameters were examined as follows: (i) electrodespacing; (ii) substrate related parameters (e.g. width); and (iii) MCNPfilm related parameters (e.g. capping ligand). In order to determine theelectrodes' spacing effect, ETP-MCNP layer was casted on electrodespacing ranging from 0.5-3 mm. The error bars are the standard deviationof 3 tested sensors for specific electrode spacing. FIG. 12A shows thatthe spacing between the electrodes has a negligible effect on the loadsensitivity. In contrast, the spacing between the electrodesdramatically changed the baseline resistance. For example, ETP-MCNP filmcasted on electrodes spacing of 1 mm showed a typical baselineresistance of 4MΩ, while a similar ETP-MCNP film casted on 3 mmelectrodes spacing showed a baseline resistance of 8MΩ (FIG. 12A).Without being bound by any theory or mechanism of action, it iscontemplated that the load sensitivity is independent on the baselineresistance. Images of the electrodes structure are presented in theinset of FIG. 12A.

FIG. 12B demonstrates that it is possible to control the loadsensitivity, using ETP-MCNP layer casted on Kapton® 127 having differentsubstrate dimensions. The error bars in the figure are the standarddeviation of 3 repetitions of the same sensor that is located on asubstrate having specific dimensions. By cutting the substrate widthfrom 30 mm to 10 mm, the load sensitivity was improved by a factor of3.5.

An additional factor which controls the sensitivity of MCNP-basedflexible sensors is provided by changing the capping MCNP layer. TheMCNPs' organic ligands determine the chemical bonds' type and strengthbetween neighboring MCNPs thereby affecting the load sensitivity. Thetunneling decay constant which determines the change in resistance isalso affected by the capping ligands. FIG. 12C presents the change inload sensitivity when replacing the capping ligand from ETP tonitro-4-trifluoro-methylbenzenethiol (NTMBT) and casting both MCNPS on 5different substrates (represented in the x axis by their Young'smodulus, E, and by their moment of inertia, I). The error bars are thestandard deviation of 3 similar sensors. There is a positive correlationbetween the load sensitivity and the properties of the substrate forboth ETP-MCNP and NTMBT-MCNP films. Nevertheless, all NTMBT-MCNP sensorsexhibited lower load sensitivities.

Hence, by adjusting the substrate width and/or changing the cappingligand in the MCNP sensor, a control over the load sensitivities can beobtained.

Example 5: Flexible MCNP Sensors as Strain Gauges

FIG. 13 shows the Gauge Factor (GF) of ETP-MCNP sensors (asterisks). GFmeasurement characterizes the sensitivity of the sensors as straingauge, viz. the ratio between ΔR/R_(b) and ∈. The GF is the slope oflinear fit of the sensors' relative response curves as a function of thestrain. In the bending setup, the strain is proportional to thesubstrate thickness and the GF is inversely proportional to thethickness of the substrate. FIG. 13 shows an inverse linear correlationbetween the GF and the thickness of the substrate. A GF of 250 could beachieved with ETP-MCNP films deposited on thin substrates (36 μm). ThisGF value is at least two times higher than previously reportednanoparticle-based strain gauges presented by hollow circles in FIG. 13and Table 2.

TABLE 2 Gauge sensors Nanoparticle diameter (nm) GF Substrate 14 35-41PET^((a))125 μm^((c)) 18 135 PET^((a)) 125 μm^((d))  4 10-20 LDPE^((b))560 μm^((e)) 18 100 photoresist 140 μm^((f)) 2-5 50-250 (substratedepended) Variety of substrates ^((a))PET = Polyethylene terephthalate^((b))LDPE = Low-density polyethylene ^((c))Farcau et al., ACS Nano2011, 5, 7137-7143 ^((d))Tsung-Ching et al, J. Disp. Tech. 2009, 5,206-215 ^((e))Vossmeyer et al., Adv. Funct. Mater. 2008, 18, 1611-1616^((f))Herrmann et al., Appl. Phys. Lett. 2007, 91, 183105

Demonstrated herein is the use of the sensors and matrix of the presentinvention as highly sensitive strain gauges. Commercial strain gaugeshave typical gauge factor of 2. MCNP Strain gauges have adjustable gaugefactor that is affected and can be controlled by the substratethickness.

Example 6: Fatigue Properties of Flexible MCNP Sensors

The fatigue properties over a large number of bending cycles were testedusing three sensors on flexible Kapton® 127 substrate and ETP-MCNP asthe sensing layer. The sensors were subjected to strains of 0.3% for10,000 cycles. In one of the sensors, the baseline resistances changeddramatically and, therefore, the sensor was excluded. The other twosensors (S1 and S2) showed a drift in baseline resistance uponincreasing the number of bending cycles (FIGS. 14A-14B). The maximumdrift in the baseline resistance was ˜9%. Without being bound by anytheory or mechanism of action, while part of the drift could beattributed to the sensor per se, at least some of the drift could beattributed to changes in the temperature and relative humidity duringthe measurement. In contrast to the baseline resistance, the ΔR/R_(b)changed only slightly (2%) after 10,000 bending cycles. Thus, it isshown that the ETP-MCNP sensors exhibit excellent fatigue properties.

Example 7: Temperature and Humidity Sensing with Flexible MCNP Sensors

The possibility to integrate temperature and relative humidity (RH)sensing capabilities using the MCNP-based touch platforms was examinedon an ETP-MCNP sensor mounted on a PET substrate. In order to test thesensor's responses to temperature and RH, the sensor was placed in avacuum chamber having a controllable environment. The temperature and RHwere altered separately, and the corresponding ΔR/R_(b) was monitored.FIG. 15A presents the ΔR/R_(b) of the sensor upon elevation of thetemperature at a constant RH level of 20% (FIG. 15A, inset). TheΔR/R_(b) decreased exponentially with temperature (Wuelfing et al., J.Phys. Chem. B 2002, 106, 3139-3145). For practical purposes, thenormalized resistance decreased by ˜1% with each 1.66° C. increase inthe temperature within a temperature range of 23-39° C. FIG. 15B showsΔR/R_(b) of an ETP-MCNP-based sensor in a humidity region that exists inmost environmental applications (5-60% RH). The sensor was tested at aconstant temperature of 25.5° C. (FIG. 15B, inset). There exists anapproximate linear increase in the sensing signal as a function of RHlevels, with sensitivity that is down to a single percent RH.

Hence, it is contemplated that the sensitivity of the ETP-MCNP-basedsensor is high enough to detect temperature fluctuations with aresolution less than 1° C. and humidity fluctuations with resolution of˜1% RH using a linear approximation of the sensor relative response. Thesensors and platform of the present invention could therefore be usede.g. as a human body thermometer or sense a heat source in the vicinityof an artificial or electronic skin, without the need for touching theobject.

Example 8: Touch Sensing Application

A demonstration of the ability of the MCNP sensors as touch sensors wasperformed by encoding letters using Morse code. Morse code is acombination of long and short pulses (lines and dots) that encode theentire alphabet and 10 digits (FIG. 16A). By pressing a finger on top ofthe sensor for short and long periods, a detection of these signals oneach of the sensors was obtained. The electrical signal is translated toinformation on the pressure magnitude and duration of the pressure.Based on this mode of operation, two different signals (a short responsein resistance which is defined as a dot, and a long response inresistance which is defined as a line) were obtained (the pressure wasroughly estimated as a single KPa). A sensor of ETP-MCNP deposited on125 μm thick PET substrate was used. The sensing layer of ETP-MCNP wasfacing down during the pressing so that no direct contact between thefinger and the ETP-MCNP layer was formed. In this manner, the effect ofthe skin humidity and temperature on the sensing is minimized. Pressingon ETP-MCNP film that is deposited on 125 μm thick PET substrateproduced robust, precise and repeatable signals (FIG. 16B). Similarresults were obtained using DT-MCNP-based pressure sensors. Pressing onsimilar ERP-MCNP film that is deposited on a different substrate, namelya 36 μm thick Mylar®, produced ×20-30 times higher responses (FIG. 16C).It is thus contemplated that the substrate's thickness largely affectssensor's responses.

It is therefore contemplated that load sensitivity can be adjusted byusing different substrates. Accordingly, it is possible to design sensormatrices that are sensitive to different load ranges (e.g. suitable forsmall children as well as adults). Additional applications includeintravascular neurosurgery where the sensing of load lower than 200 mgare required, a seat-belt sensor having small load sensitivity totransduce at loads larger than 1,000 Kg, or scoliosis surgery wherehigh-load stress sensors are required.

Most touch panels today are based on an on/off sensing mechanisms werethe devices are able to sense applied load but with no ability todetermine the load (Walker, J. Soc. Info. Disp. 2012, 20, 413-440). Theplatform unit of the present invention has the capability of not merelyto sense touch but also to sense the load magnitude. Using a variety ofsubstrates allows tuning the sensing properties to specific load rangesthat are required for a specific application.

Example 9: MCNP-Based Sensing Platforms for Integrated Measurement ofPressure, Temperature and Humidity

Sensing various parameters (e.g., pressure, temperature, humidity) froma complex sample using a single flexible sensing platform isdemonstrated herein. A prototype based on MCNP technology was preparedand its abilities to measure the surrounding temperature, relativehumidity and applied load were estimated. Different substrates were usedin order to eliminate the load sensing from part of the sensors, anddifferent capping ligands were chosen to isolate the sensing of relativehumidity or temperature. Two sensors were fabricated by casting ETP-MCNPand NTMBT-MCNP on silicon dioxide with evaporated interdigitated goldelectrode. A third sensor was fabricated by casting ETP-MCNPs on a PETsubstrate with 1 mm electrodes spacing as illustrated in FIG. 17.

Temperature and humidity were calculated using the inflexible sensors.For sensing relative humidity, a perforated NTMBT-MCNP film was used asdescribed in Segev-Bar et al., J. Phys. Chem. C. 2012, 116, 15361-15368;the content of which is hereby incorporated in its entirety. This sensorhas a large negative response (up to 80%) to increasing levels of RH dueto ionization mechanism. As can be seen in FIGS. 18A-18B, the relativeresponse of NTMBT-MCNP to 55% RH is about −70% while the maximumrelative response to temperature in the tested range (23-38° C.) was15%. In order to sense mainly temperature changes, a high concentratedETP-MCNP solution (50 mg/ml) was casted on silicon dioxide substrate,resulting in a film of 500 nm thickness (estimated by AFM). The film'sthickness was higher than the thickness of the evaporated goldelectrodes (350 nm) which may result in possible swelling (Steinecker etal., Anal. Chem. 2007, 79, 4977-4986). As seen in FIGS. 18C-18D, theresponse of the ETP-MCNP layer on the silicon dioxide substrate torelative humidity was within the noise range (±1%) for the entirerelative humidity range (22-63% RH), while the relative responsedecreased when increasing the temperature (ΔR/R_(b)˜1.35% for each 1° C.change).

The prototype platform was exposed to different temperature and relativehumidity cycles controlled by air conditioning in a room. The relativehumidity range was 33-60% and the temperature range was 15-22° C. Therelative humidity was modeled by a linear fit in FIG. 18A and thetemperature was modeled by an Arrhenius fit in FIG. 18D. The averageerrors from the values measured by external sensors of 6 differentcycles are summarized in Table 3. When averaging all cycles, thetemperature average error was 4.8%±1.4% and the RH average error was9.3%±7%.

TABLE 3 Summary of the accuracy for measuring temperature and RH usingS1 and S2 Temperature RH average Cycle average error (%) error (%) 117.7 ± 2.6  5.8 ± 6.9 2 2.3 ± 1.2  20 ± 5.7 3 0.7 ± 0.6 10.7 ± 9.8  4  8 ± 1.4 5.8 ± 6   5 9.4 ± 1.5 6.6 ± 7.3 6 10.2 ± 1.3 7.8 ± 6.2

For assessing the performance of the prototype platform in sensing load,an unknown load was applied on the flexible ETP-MCNP sensor. For thispurpose an algorithm that accounts for the temperature, RH and load isrequired. In general, the change in resistance of a given sensor is afactor of three parameters: temperature, RH and load. The effect of eachparameter may be linear or non-linear. However, as disclosed herein, itis possible to model and measure a sensor's resistance due to changes inRH and temperature under a given load. To demonstrate the ability toeasily model the effect of RH and temperature, several experiments wereperformed. The correlation between temperature and RH on the sensor'sresistance was established by exposing the sensor to a range oftemperatures (23-38° C.) at 2 different constant RH conditions (FIG.19A) and exposing the sensor to a range of RHs (22-63%) at 3 constanttemperatures (FIG. 19B). FIG. 19A shows the Arrhenius dependence of thesensor's response to various temperatures. The lines of the 2 differentRH conditions are parallel. For small temperature ranges (˜5° C.), thesensor's temperature dependence can be approximated as linear. FIG. 19Balso exhibits mostly linear and parallel responses upon increasing RHlevels (excluding the step in 20% RH at 30° C.). Since it was notpossible to maintain constant conditions for RH >25% when changing thetemperature. it is contemplated that this hehavinr represents the entiretested range (Konvalina et al., ACS Appl. Mater. Interf. 2012, 4,317-325). The dependence of the ETP-MCNP sensor's response ontemperature (T) and relative humidity (RH) can be approximatelydescribed in the following equation:R=R _(baseline) +ΔR _(RH) ·RH+ΔR _(T) ·Twhere R is the measured resistance of the sensor; ΔR_(RH) is the changein resistance per unity change in the relative humidity; ΔR_(T) is thechange in resistance per unity change in the temperature; andR_(baseline) is the extrapolated resistance under zero temperature andRH. A linear model was used for simplicity. Based on this equation, theresponse of the flexible ETP-MCNP sensor can be described as a plane inthe resistance—temperature—RH space.

The three-sensor-based prototype was measured under changingenvironmental conditions as mentioned above. The flexible ETP-MCNPsensor was examined under different loads. The response of the flexibleETP-MCNP sensor to temperature (ΔR_(T)) and relative humidity (ΔR_(RH))was different for different loads, and calculated using a solver scriptin Microsoft. The input parameters that were used are: the differentenvironmental conditions (temperature and relative humidity) and thecorresponding resistance of the flexible ETP-MCNP sensor.

FIG. 20 describes the different dependencies of the flexible ETP-MCNPsensor at the temperature and relative humidity under zero load (Load0), load of 3 gr (Load 1) and a load of 6 gr (Load 2). The temperatureand relative humidity were calculated by the inflexible ETP-MCNP andNTMBT-MCNP sensors (FIGS. 18A-18D and 19A-19B). As can be seen in FIG.20, the relative response to temperature and relative humidity changedwhen different loads were applied (e.g. ΔR_(RH) and ΔR_(T) weredependent on the load).

TABLE 4 Calculated and applied loads on an ETP-MCNP sensor deposited ona PET substrate. Applied Calculated load Load 18.7° C., 47% RH 19.7° C.,45% RH 21.4° C., 43.5% RH 3 gr 2.42 gr  2.8 gr 3.07 gr 6 gr  6.7 gr 6.68gr 6.08 gr

The accuracy of the model was estimated by measuring the loadsensitivity of the ETP-MCNP sensor on PET substrate at specifictemperatures and RHs, calculating the relative response of the sensor atthese environmental conditions based on the plans that are presented inFIG. 20, and calculating the applied force based on the data. Theresults are summarized in Table 4. The results clearly demonstrate theability of the model to estimate the load with less than 20% variance.

The matrix prototype presented herein uses different MCNP on inflexiblesubstrate in order to sense temperature and humidity in an un-conjugatedmanner (were a single sensor senses only either temperature or relativehumidity). A post measurement algorithm was used for the flexibleETP-MCNP sensor in order to isolate load sensing from other parameters(temperature and humidity). When load was applied, the enlargingdistance between the nanoparticles changed the surface coverage whichresulted in a change in morphology. These changes affect the MCNP sensorresponse. In instances where the effect of temperature and RH onresistance is not linear, it is possible to model the correlation, anddraw representative non-linear planes that would enable the measurementsof the desired parameter.

Example 10: Integration of Load, Temperature and RH Sensors (3 in 1) ViaLayer-by-Layer Deposition

Gold nanoparticles coated with dodecylamine (DA-GNPs) were deposited viathe layer-by-layer (LBL) technique (Joseph et al., J. Phys. Chem. C.2007, 111, 12855-12859; and Vossmeyer et al., Adv. Funct. Mater. 2008,18, 1611-1616) on a Kapton® substrate having two electrode pairs withdifferent shapes and spaces (S1 and S2). S1 had an interdigitatedstructure of 10 pairs of Au electrodes (100 μm width and 100 μm spacingbetween adjacent electrodes). S2 and S3 had 2 electrodes with 100 μmspacing between them. The use of different pairs of electrodes resultedin different baseline resistances for S1 and S2 (˜150 KΩ for S1 and˜4100 KΩ for S2). Hence, by fabricating the environmental sensors usingdifferent electrode structures, different responses to temperature andhumidity are obtained. S3 was placed facing down towards the tableassuring partial shielding from the environment. A small window engravedinto the substrate allowed physical sinking when the sensor was pressedtowards the table (FIG. 21A). The sensors' resistance was measured atroom environmental conditions. The temperature and relative humidity ofthe room were recorded by separate (external) sensors. Separating thethree features (pressure, relative humidity and temperature) wasperformed as follows: Both S1 and S2 were measured under varyingconditions. The experimental temperature range was 21.5° C.-26° C. andthe relative humidity range was 55-85%. Post-measurement algorithmiccalculations were used to calculate the RH and T parameters while thethird environmental protected sensor was set to simultaneously sensetouch. The dependency of each sensor i on the temperature (ΔR_(iT)) andrelative humidity (ΔR_(iRH)) was different due to the differentelectrodes' structure, and calculated using a solver script in MicrosoftExcel based on 13 measurement sets. As an input, the differentenvironmental conditions (temperature and relative humidity) and thecorresponding resistance of each of the two sensors were used in thefollowing equation:R _(i) =R _(ibaseline) +ΔR _(iRH) ·RH+ΔR _(iT) ·Twhere R_(i) is the measured resistance of sensor i under certain RH andtemperature (T) conditions, and R_(ibaseline) is the extrapolatedresistance under zero temperature and RH. Based on the two sensors thatcreate different planes in the resistance—temperature—RH space, thetemperature and the relative humidity was calculated in an injectivemanner (FIG. 21B).

TABLE 5 Summary of the model's accuracy for temperature and RH sensingwith S1 and S2 Measured Calculated temperature temperature % MeasuredCalculated Deviation (° C.) (° C.) deviation RH (%) RH (%) (%) 22.1 220.5 59.2 58.6 1 23.7 23.3 1.7 82 84.7 3.3 25.3 25.4 0.4 83 83.1 0.1

In order to test the accuracy of the received model, three additionalpoints of resistance under different environmental conditions weremeasured by an external sensor and calculated through the fittedequations. The results are presented in Table 5. The middle sensorfacing down (S3) was less sensitive to the variations in humidity andtemperature, where the effect on the resistance was less than 1%throughout the entire experiment. In comparison, when applying pressuresof about 15 KPa, the response due to bending of the substrate was about2% (FIG. 21C). Thus, it is possible to sense pressure using S3 withdetection limit of 15 KPa, since the effects of temperature and relativehumidity on the sensor are insignificant when comparing the magnitude ofthe signal that was obtained by the applied pressure. Thus, forpressures higher than 15 KPa, the noise as a result of changing theenvironmental conditions is negligible and the pressure can be easilymeasured. The model can estimate the surrounding temperature andrelative humidity (Table 5). Therefore, by combining three sensors withsimilar nanoparticle coating and controlling the electrodes shape anddirection it is possible to measure all three parameters.

Hence, by using an array of 3 sensors in which the load sensor isprotected from environmental effects and the other two sensors areprotected from mechanical deflection, multi-parametric sensing can beobtained. These results demonstrate the possibility of producing andintegrating temperature and humidity sensors as part of an artificial orelectronic skin application based on MCNPs. Thus, it is possible to usea single (or similar) MCNP chemistry with various substratestructures/designs to achieve multi-parametric sensing such astemperature, relative humidity and load, on the same platform.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and sub-combinations of various featuresdescribed hereinabove as well as variations and modifications.Therefore, the invention is not to be constructed as restricted to theparticularly described embodiments, and the scope and concept of theinvention will be more readily understood by references to the claims,which follow.

The invention claimed is:
 1. A platform unit for detecting a parameterselected from the group consisting of pressure, temperature, humidityand a combination thereof, the platform unit comprising: a plurality ofsensors, wherein each of the sensors comprises metallic nanoparticlescapped with an organic coating, wherein the plurality of sensorscomprise: i) a dual temperature and humidity sensor being deposited on asubstantially flexible or rigid substrate; or ii) a dual pressure andhumidity sensor being deposited on a substantially flexible substrate;or iii) a dual pressure and temperature sensor being deposited on asubstantially flexible substrate; or iv) two sensors, wherein one sensoris a dual pressure and humidity sensor being deposited on asubstantially flexible substrate, and the other sensor is a dualpressure and temperature sensor being deposited on a substantiallyflexible substrate.
 2. The platform unit according to claim 1 furthercomprising at least one of: i) a plurality of electrodes comprising anelectrically conductive material, wherein the plurality of electrodesare coupled to each sensor and are used for measuring the signalsgenerated by the sensors; or ii) a detection means comprising a devicefor measuring changes in resistance, conductance, alternating current(AC), frequency, capacitance, impedance, inductance, mobility,electrical potential, optical property or voltage threshold, or iii) afilm, wherein the film is configured to block at least one sensor fromgenerating a signal in response to a change in humidity, or iv) ananalyte sensor, wherein the analyte sensor is configured to sense ananalyte adsorbed thereon and to generate an electrical signal inresponse thereto.
 3. The platform unit according to claim 1, whereineach sensor is configured in a form selected from the group consistingof a capacitive sensor, a resistive sensor, a chemiresistive sensor, animpedance sensor, and a field effect transistor sensor.
 4. The platformunit according to claim 2, wherein the film is characterized by athickness ranging from about 1 μm to about 1000 μm, and wherein the filmis selected from the group consisting of an epoxy resin, a siliconresin, a polyamide resin, a polyimide resin, a poly(p-xylylene) resinand a combination thereof.
 5. The platform unit according to claim 1,wherein the substantially flexible substrate is characterized by widthsin the range of about 0.01-10 cm and thicknesses in the range of about20-500 μm.
 6. The platform unit according to claim 1, wherein thesubstantially flexible substrate comprises a polymer.
 7. The platformunit according to claim 6, wherein the polymer is selected from thegroup consisting of polyimide, polyamide, polyimine, polyethylene,polyester, polydimethylsiloxane, polyvinyl chloride, and polystyrene. 8.The platform unit according to claim 1, wherein the substantially rigidsubstrate is selected from the group consisting of metals, insulators,semiconductors, semimetals, and combinations thereof.
 9. The platformunit according to claim 1, wherein the metallic nanoparticles areselected from the group consisting of Au, Ag, Ni, Co, Pt, Pd, Cu, Al,and combinations thereof or wherein the metallic nanoparticles aremetallic alloys selected from the group consisting of Au/Ag, Au/Cu,Au/Ag/Cu, Au/Pt, Au/Pd, Au/Ag/Cu/Pd, Pt/Rh, Ni/Co, and Pt/Ni/Fe.
 10. Theplatform unit according to claim 1, wherein the organic coatingcomprises compounds selected from the group consisting of alkylthiols,arylthiols, alkylarylthiols, alkylthiolates, ω-functionalizedalkanethiolates, arenethiolates, (γ-mercaptopropyl)tri-methyloxysilane,dialkyl disulfides and combinations and derivatives thereof.
 11. Theplatform unit according to claim 1, wherein the signal generated by eachparameter is extracted using pre-measurement calibration,post-measurement calculation or a combination thereof.
 12. The platformunit according to claim 1, wherein the plurality of sensors comprisecontinuous and discontinuous regions of metallic nanoparticles cappedwith an organic coating.
 13. The platform unit according to claim 12,wherein the discontinuous regions comprise voids ranging in size fromabout 10 nm to about 500 nm.
 14. The platform unit according to claim13, wherein the discontinuous regions comprise between about 3% andabout 90% voids.
 15. The platform unit according to claim 1, integratedon electronic or artificial skin surface.